ReactOS denies those accusations. If it's true and proved, probably users should stop using it, but until it's proved, I don't think that it's an issue. Like you've got some software, you checked its license, it's open source reimplementation of Windows, sounds good. For example Valve uses wine to run games on Linux, it's pretty legit.
WINE and ReactOS are separate projects and the allegations in the Quora post are specific to ReactOS. WINE doesn't handle NT kernel internals; it reimplements public Windows APIs and proxies kernel functionality to the host userland (usually GNU+Linux+X11 but occasionally Darwin+AppKit).
The main existential threat to WINE would be the Oracle/Google case being decided (sometime before June). If that winds up creating adverse precedent to Google's case, the entire Free Software movement will be negatively impacted. Actually, it'll be like 100 SCOs, given how much of our Free foundations are functionally-compatible reimplementations. We'll lose pretty much everything except scripting language runtimes, Rust, and C compilers; and there would surely be no way to do something like WINE if SCOTUS decides to trample all over the merger doctrine and starts granting copyright on functionality.
BSD networking was distributed under a very permissive license, so that would extend to any new APIs included in BSD. You'd have to argue that the BSD license doesn't cover API rights, which would basically be like trying to argue that it's not really permissively licensed at all.
You'd probably have a better argument for GPL violation for non-GPL reimplementations, but I'm not aware of that many people doing proprietary reimplementations of Linux APIs. Hell, even Microsoft stopped trying that when they moved to WSL2.
